I wouldn't bother using that cage for a bearded dragon. It isn't practical at all as it would last maybe a couple months for a baby bearded dragon then you will need to get it a bigger cage of 4'x2'x2' or bigger for a single bearded dragon.
What I would use that cage for is crested geckos, gargoyle geckos, red eyed tree frogs and other smaller arboreal species of lizards, geckos or amphibians. It may be ok for some snakes as well.
If you kept the divider in (I am assuming the total size of the cage is 24"X24"X18" instead of each section being that size) you could house single crested geckos per section, dart frogs and other small lizards, maybe some very small snakes. I would remove the divider completely myself and use the cage for crested geckos, maybe a breeding group of one male and two or three females. Or you can keep the divider in and have two crested geckos (may be good to do th is with a couple juvies till they are old enough to sex then if you have a male/female or female female group, you can remove the divider and have them housed together.
If both sections are the stated dimensions, then it may be ok for a bearded dragon for a little bit but the all plexi glass makeup will not do very well for too long anyway.
If you do want to use it for a bearded dragon baby temporary, I suggest cutting out a large opening on the top and replacing with aluminum screen so you can place a hooded light fixture for a heating bulb and and either mount a small under cabinet fixture underneath the lid *beside/behind the basking spot but stretching as much as the total length of the cage as possible). Remove the florescent tube the under cabinet fixture comes with and replace with a UVB tube. Don't put on the plastic cover that usually covers the bulb on the under cabinet fixture. This will just block all the uvb light rays and most of the light anyway.
You probably can screw the fixture directly to the plexiglass top, inside the cage (pre drill and use a nut to secure the screw or you can use a board instead and just cut a hole in the top big enough for the fixture, so the bulb is shinning into the cage. I will also orient the cage so the height is 18" thus giving you 2'x2' of floor space, which is better for bearded dragons than height. Also, just remove that divider, you won't need it for a bearded dragon anyway.
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PHLdyPayne